Screening and Identification of Naphthalene-Degrading Bacteria from the Coastal Regions of Makran Sea

Makran Sea and its coastal areas are one of the richest marine ecosystems in the world. The primary purpose of this research was to study Naphthalene-degrading bacteria in some coastal areas of Makran Sea. Four coastal areas of Makran Sea were selected and marine samples were taken from each. Naphthalene-degrading bacteria were enriched in ONR medium in the shaker incubator for seven days with Naphthalene as the sole carbon source. This process was carried out in two separate passages. Some screening analyses were conducted for the selection of the best Naphthalene-degrading strains such as growth assay (OD_{600 nm}), Naphthalene-degradation (GC), cell surface hydrophobicity (BATH), and emulsion production (E₂₄). The predominant strain in Naphthalene-degradation was identified by molecular method. The results of this study showed that the quantity of bacteria present in different regions of Makran Sea varies. An example of this was the highest quantity of Naphthalene-degrading bacteria which were observed in Jask Port, however, the level of heterotrophic bacteria was the highest in Konark Station in comparison to other areas. In this research 65 Naphthalene-degrading bacteria were isolated from collected marine samples. Screening analysis confirmed that 9 strains were more efficient in Naphthalene-degradation and these strains were selected for further study. The best Naphthalene degrader isolate in this study was HS-2 strain, which according to molecular identification results belongs to Shewanella alga. This strain was an emulsifier producer (E₂₄: 88%), and had high cell surface hydrophobicity (BATH: 36%) and was able to degrade Naphthalene in 3000 ppm concentration (70.8%). The results of this research confirmed that Makran marine ecosystem has effective bacteria in the degradation of Polycyclic Aromatic Compounds (PAH). By using these bacteria in the field, it is possible to reduce aromatic pollution in these coastal areas.